Heat-sensitive high molecular weight resistors

ABSTRACT

HEAT-SENSITIVE HIGH MOLECULAR WEIGHT RESISTORS (PLASTIC THERMISTORS) CAPABLE OF PROVIDING ELECTRIC CONDUCTIVITY DUE TO CHARGE TRANSFER BONDS WHICH ARE COMPARABLE IN MOLDABILITY AND FLEXIBILITY TO THE PLASTICS OF GENERAL USE AND ARE ELECTRONIC CONDUCTIVE. THE RESISTORS ARE BEST SUITABLE AS HEAT-SENSITIVE RESISTORS FOR CONTROLLING THE TEMPERATURES OF ELECTRIC BLANKETS,A ND ARE REDUCED IN RESISTANCE VALUE TO 1/3-1/4 PER TEMPERATURE VARLIATION OF 10*C. WITHIN THE TEMPERATURE RANGE OF -30* TO+120*C. THEY CAN WITHSTAND HEAT RESISTANCE TEST AT 120*C. FOR 300 HOURS.

Jan. 4, 1972 KAZUMASA YAMAMoTo ETAL 3,632,52

HEAT-SENSITIVE HIGH MOLECULAR WEIGHT RESISTORS Filed July 29, 1968 3Sheets-Sheet l INVENTORS #azur/sfr yn/YMorv/Hml amg ATTOR NE Y.S

Jan', 4, 1972 KAZUMASA YAMAMOTO ETAI- 3,632,525

HEAT-SENSITIVE HIGH MOLECULAR WEIGHT RESISTORS G e. B g/JHWX; r Q i a,

5 2 LL L Q l l Q Q *D Q (fa/af) 4407;/ 7m@ INVENTORS ATTOR NEYS Jan- 4,1972 KAZUMASA YAMAMoTo ETAL 3,632,526

HEAT-SENSITIVE HIGH MOLECULAR WEIGHT RESISTORS Filed July 29, 1968 3Sheets-Sheet 3 @WHW/@NAL EXAMPLE/ CavL/Hvr/ONAL EXAMHE 4 L l /80 00(CoM/mmv EXAMPLEZ? /20 /40 TEMPS/QA z/Rf ("C (ww) MOH 791ml INVENTORS/mzu #05H yfm mfoml H/Ru/ #M160 wm'nmL .SH/Marsan, Tow/o sH/mzu.

United States Patent C1 hee Patented `lari. 4, 1972 ABSTRACT F THEDISCLOSURE Heat-sensitive high molecular weight resistors (plasticthermistors) capable of providing electric conductivity `due to chargetransfer bonds which are comparable in moldability and ilexibility tothe plastics of general use and are electronic conductive. The resistorsare best suitable as heat-sensitive resistors for controlling thetemperatures of electric blankets, and are reduced in resistance valueto /s-lr per temperature variation of C. Within the temperature range of30 to +120 C. They can withstand heat resistance test at 120 C. for 300hours.

This invention relates to heat-sensitive high molecular weight resistorswhich are not only electronic conductive but also comparable inmoldability and flexibility to the plastics of general use.

As temperature-detecting processes for the detection or control oftemperatures, there have heretofore been employed processes of detectingtemperatures according to variations in resistance values of metal wireresistors or metal oxide thermistors, or according to variations inpolyehylene and the like which detect temperatures according tovariation in resistivity due to degradation of dielectric breakdownstrength thereof at elevated temperatures. A drawback common to theseresistors, however, is that since the electroconductive mechanismsthereof are ionic conductive, it is diicult to detect temperatures ifdirect current is applied thereto.

It is an object of the present invention to provide novel heat-sensitivehigh molecular Weight resistors (plastic thermistors) which areexcellent in moldability, ilexibility and mechanical properties andwhich are usable by application of direct current.

The heat-sensitive high molecular weight resistors of the presentinvention are thermistors which do not cause polarization even whendirect current is `applied thereto and are stable in electricresistivity even at elevated temperatures. Further, the presentresistors are comparable in moldability and flexibility to the plasticsof general use. Accordingly, when molded into lines, they are usable forthe temperature detection of heat-sensitive heating electric wires ofelectric blankets, carpets and the like, and for the temperaturedetection of re detectors and air-conditioners. Further, when moldedinto the form of sheets, they are usable for the temperature detectionoflloor heaters, spherical surfaces of hot rollers and the like. Thus, theresistors of the present invention are expected to nd limitlessindustrial uses for temperature detection. Further, they are high intemperature detection sensitivity and hence are excellent plasticthermistors prominent in moldability and flexibility.

=PRIOR ARTS A comparison in detection sensitivity between the plasticthermistors of the present invention and metal wire resistors,thermocouples and metal oxide thermistors which have heretofore beenused as temperature detection elements is as shown in Table 1.

TABLE 1.-SENSITIV'ITY OF TEMPERATURE DETECTION MATERIALS Plasticthermistor do thermoelectromotive force of thermocouples, or accordingto variations in geometrical shape of bimetal. These processes areexcellent for local temperature detection, but suffer from such fataldrawbacks that for the detection of average temperature in a definiteatmosphere, a plurality of elements are required to be used, and thatthey are low in variation ratio of signals towards temperaturevariations.

In order to overcome said drawbacks, heat sensitive high molecularweight resistors, which are freely moldable into the form of lines orsheets, have recently been developed and are applied, in practice, tosecurity mechanisms for electric blankets, electric carpets and thelike. As heat-sensitive high molecular weight substances usable for saidpurposes, there are high polymer compositions prepared by adding a smallamount of surface active agent to such a matrix as plastisized polyvinylchloride which detect temperatures according to variation in resistivityof resistance temperature characteristics thereof, and nylon,

Thus, the present plastic thermistor' has a sensitivity of l0-200 timesthe sensitivity of the conventional temperature detection elements.Although the present plastic thermistors are usable at such limitedtemperatures ranging from 30 C. to +120 C., they show high detectionsensitivity at temperatures within said range. The conventionaltemperature detection elements cannot be subjected to any furtherprocessing than the primary processing and, moreover, are low inflexibility. Accordingly, they are limited in shape. In contrastthereto, the present plastic thermistors are same in moldability andflexibility as the thermoplastics of general use, e.g. plastisizedpolyvinyl chloride, and hence can be processed into optional shapes.Further, the conventional thermocouples and thermistors are small indetection portion and are low in heat capacity, and hence displayprominent effects for local temperature detection However, the plasticthermistors of the present invention have a volume resistivity at 30 C.of 5.8 10lf-3.l l012 o (Q cm.), and hence are usable with broadelectrode surfaces. The present plastic thermistors display greatcharacteristics for temperature detection broader in surface area orspace than the conventional local temperature detection, and they havebeen invented for the above purpose.

For example, when applied as heat-sensitive heaters of electricblankets, the plastic thermistors make possible such temperaturedetection means that not only the average temperature but also any localunusual temperature increase within the blankets can be detected. Asmentioned previously, the plastic thermistors are moldable and hence canbe processed into any such shapes as lines, ribbons and sheets.Accordingly, they can be used in most effective shapes for the purposesof appliances, which require temperature detection. When applied toelectric blankets, the present plastic thermistors having suchepoch-making characteristics will drive out the temperature controlsystems using bimetals which have heretofore been employed.

Electronic conductive polymers comparable in processability, mechanicalproperties and flexibility to the thermoplastics of general use have notbeen invented yet. However, several attempts for the manufacture ofmoldable and flexible thermistors have been made as explained below.

(l) An attempt in which a good conductor for electricity such as a metalpowder or carbon black is dispersed in a high molecular Weight substanceto impart electric conductivity thereto by inter-particle contact. Whenthe amount of conductor added, according to the above process, is morethan a certain amount, there is obtained a thermistor which issubstantially identical in resistance value and temperature coefficientof thermistor With the added conductor. If the amount added is madesmaller, a thermistor high in resistance value and in temperaturecoeicient of thermistor is obtained, but the resistance value isunstable and is low in reproductivity. Particularly at elevatedtemperatures, the interparticle contact becomes unstable due tomolecular movement,

(2) An attempt in which, onto the surface of carbon black, a monomersuch as styrene, ethyl acrylate or the like is graft-copolymerized tocover the surfaces of carbon particles with a polymer, thereby providingprocessability. This process can give a thermistor low in resistance andin temperature coefficient of thermistor, but is not suitable for massproduction.

(3) An attempt in which a surface active agent is kneaded with anddispersed in an insulating high molecular weight material. This processcan give a thermistor which is ionic conductive and which is high bothin resistance value and in temperature coeicient of thermistor. Thisthermistor is utilized as a heat-sensitive high molecular weightresistor.

Usable as the surface active agent are stearyl dimethyl benzyl ammoniumchloride, cetyl dimethyl benzyl arnmonium chloride, N-lauryl imidazoliumbromide, tetrabutyl ammonium picrate, etc.

Usable as the insulating high molecular weight material are polyamide,polyethylene, butadiene-acrylouitrile copolymer, polyvinyl chloride,etc.

Thermistors of this type have such drawbacks that since they are ionicconductive, they cannot be used unless alternating current is applied,and that they become unstable when continuously used for a long periodof time.

(4) An attempt in which a charge transfer complex, which is an organicsemiconductor, is polymerized to provide moldability.

A charge transfer polymer comprising poly-2-vinyl pyridine as a donorand tetracyanoparaquinodimethane (TCNQ) as an acceptor has a volumeresistivity of 1.0 103 Q cm. and a temperature coe'lcient of thermistorof 2,000 K., but is low in mechanical strength and Iilexibility, andhence is not put into practical use at present.

CONSTRUCTION The plastic thermistors of the present invention are highmolecular weight semiconductors comprising high polymers having highpolymer portions which provide moldability and flexibility and chargetransfer bonds which provide electric conductivity. They have a volumeresistivity of at least 102 Q cm. and a temperature coetcient ofthermistor of at least 1,000 K. Constructions of the present plasticthermistors and processes for the production thereof are detailed belowwith reference to examples.

(l) Electronic conductive polymer-type thermistors Thermistors of thistype are plastic thermistors which are composed of high molecular weightcharge transfer complexes formed from a processable, moldable andilexible high molecular weight electron donor and a high molecularweight electron acceptor, or which are composed of charge transfercomplexes formed from an electron donor and an electron acceptor, eitherone of said donor and acceptor being a processable, moldable and exiblehigh molecular weight substance and the other being a low molecularweight substance. When the kinds and proportions of electron donormonomers and electron acceptor monomers in the constituents of chargetransfer complexes are varied, it is possible to obtain electronicconductive plastic thermistors having optional volume resistivity andtemperature coeicient of thermistor.

As the high molecular weight electron donor, there is used a binary orternary copolymer of an electron donor monomer, eg. 2-vinylpyridine(ZVP), 4-vinylpyridine (4VP), 1-Vinyl-Z-methylimidazole (1V2MI),N-vinylcarbazole (NVCA), N-vinylthiocarbazole (NVSCA) or N-vinylpyrrolidone (NVPy), with any of monomers capable of providingprocessability, moldability and ilexibility, c g. styrene (St.), methylacrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), butylacrylate (BA), ethylhexyl acrylate (EHA), acrylonitrile (AN), vinylacetate (VAC and octylvinyl ether (OVE), or a homopolymer of saidelectron donor monomer.

The high molecular weight electron `acceptor is a homopolymer of amonomer having properties as an electron acceptor, such as for example,trinitrostyrene, dinitrostyrene, phthalic anhydride, or maleicanhydride, or is a binary or ternary copolymer comprising, as the -rstcomponent, the above-mentioned monomer and, `as the second and/ or thirdcomponents, such monomers capable of providing processability,moldability and flexibility as exemplitied in the case of the electrondonor. As the low molecular weight electron donor, there is usedp-phenylenediamine, diphenylamine, perylene or 1naphthylamine, and asthe low molecular weight electron acceptor, there is used chloranil,bromanil, tetracyanoethylene, tetracyano-p-quinodimethane,hexacyanobutadiene, hexachlorobutadiene or tetracyanobutadiene.

Examples l and 2, described later, show complexes comprising highmolecular weight electron donors and high molecular weight electronacceptors; Examples 3 to l() show complexes comprising high molecularweight electron donors and low molecular Weight electron acceptors; andExample 1l shows a complex comprising a low molecular weight electrondonor and a high molecular Weight electron acceptor.

(2) Blend-type electroconductive high molecular Weight compositionsCompositions of this type are such that, noticing the electricconductivity of charge transfer complexes, processability, moldability,mechanical strength and exibility are intended to be provided chiefly bymatrix polymers. In the case of the compositions of this type, it isnecessary that the complexes should have been molecularly dispersed inthe matrixes in order to attain favorable electrical properties (volumeresistivity and temperature coeicient of thermistor) and, particularly,stability in electric resistivity at elevated temperatures. As thesource for providing electric conductivity, therefore, there is used ahigh molecular weight or low molecular weight charge transfer complexwhich is favorable in compatibility with an insulating high polymer tobe used as the matrix.

The charge transfer complex may be any of those in which either one orboth of the donor and acceptor are high molecular weight polymers.Usable as such charge transfer complex are:

(i) (Ethyl acrylate-styrene-Z-vinylpyridine)-TCNE complex.

(ii) (Z-ethylhexyl acrylate-styrene-2-vinylpyridine)- TCNQ complex.

(iii) (Styrene-N-vinylcarbazole)(styrenetrinitro styrene) complex.

(iv) p-Phenylenediamine-(styrene-trinitrostyrene) complex.

As the low molecular weight charge transfer complex, there is used onehaving in the molecule at least one group capable of increasingcompatibility with a matrix polymer, such as for example, an alkyl group-CnHznH (n=1, 2, 3, 40), a benzyl group a phthalodiamide ethyl group HCON-CzHia monoester phthaloyl group C O O R CON- H R=CH3, C2H5 C40H81),a fatty acid amide group (RI=CH3, C2H5 C40H31), an enedicarbonyl group-CO-'RCO, an alkylenedioxy group -O-R-O or a hydroxy alkylenecarbonylgroup HO-R-CO-. For the preparation of the blends, said charge transfercomplexes are molecularly dispersed in high molecular weight matrixes.

Usable as such high molecular Weight matrixes are polyvinyl chloride,polystyrene, ethylene-ethyl acrylate copolymers, ethylene-vinyl acetatecopolymers, styrenebutadiene copolymers, acrylonitrile-methylmethacrylate copolymers, styrene-Z-ethylhexyl acrylatebutyl acrylatecopolymers, and urethane. When these high molecular weight matrixes areblended with the charge transfer complexes, plastic thermistorsexcellent in moldability and flexibility can be produced. For uses wheremore precise molding is required, they may be blended withstyrene-butadieneacrylonitrile copolymers (ABS resins) or with epoxyresins. Detailed production procedures are described in the examples.Examples 12-15 show compositions containing high molecular weight chargetransfer complexes, and Examples 15-2l show compositions containing lowmolecular weight charge transfer complexes.

EXAMPLE 1 Charge transfer complex comprising 2-vinylpyridinestyrenecopolymer as donor and maleic anhydridestyrene copolymer as acceptor (a)Synthesis of 2-vinylpyridine-styrene copolymer: To 100 g. of toluene areadded 20 g. of vacuum distilled 2- vinylpyridine, g. of styrene and 0.5g. of azobisisobutyronitrile as a polymerization initiator. The mixtureis refluxed for 4 hours to effect polymerization. The reaction liquid isadded dropwise to 5 l. of methanol, and the resulting precipitate isrecovered by filtration and is repeatedly subjected to thoroughwater-washing. Subsequently, the precipitate is dried under reducedpressure to obtain a 2-vinylpyridine-styrene copolymer containing 23% ofZ-Vinylpyridine.

(b) Synthesis of maleic anhydride-styrene copolymer: To g. of tolueneare added y80 g. of vacuum distilled styrene, 2i() g. of maleicanhydride and `0.3 g. of benzoyl peroxide as a polymerization initiator.The mixture is refluxed for 3 hours with stirring to effectpolymerization. The reaction liquid is added dropwise to 5 l. ofmethanol, and the resulting precipitate is recovered by filtration andis repeatedly subjected to thorough water-washing. Subsequently, theprecipitate is dried under reduced pressure to obtain a maleicanhydride-styrene copolymer containing 21% of maleic anhydride.

(c) 'Synthesis of charge transfer complex: The two copolymers (a) and(b) are individually formed into 10% toluene solutions and are mixedtogether in equivalent amounts, whereby the mixture immediately becomesbrown. The mixture is then refluxed for about l hour to form a brownprecipitate. The thus formed precipitate is water-washed andvacuum-dried to obtain a high molecular weight charge transfer complexcomprising the 2-vinylpyridine-styrene copolymer and the maleicanhydride-styrene copolymer. This complex is shaped into the form of a lmm. thick sheet and is cut to a size of 50 x 50 x 1 mm. to prepare atest piece for electric resistance measurement.

EXAMPLE 2 Charge transfer complex comprising N-vinylcarbazolestyrenecopolymer as donor and polytetracyanobutadiene as acceptor (a) Synthesisof N-vinylcarbazole-styrene copolymer: To 100 g. of xylene are added 80g. of vacuum-distilled styrene, 20 g. of N-vinylcarbazole and 0.2 g. ofazobisisobutyronitrile as a polymerization initiator. The mixture isrefiuxed for 3 hours with stirring to effect polymerization. Thereaction liquid is added dropwise to 5 l. of methanol, and the resultingprecipitate is recovered by filtration and is repeatedly subjected tothorough waterwashing. Subsequently, the precipitate is dried underreduced pressure to obtain an N-vinylcarbazole-styrene copolymercontaining 20% of N-vinylcarbazole.

(b) Preparation of polytetracyanobutadiene: 50 g. of1,2,3,4-tetracyanobutadiene is dissolved in 100 g. of acetonitrile. Tothe solution, 0.1 g. of benzoyl peroxide as a polymerization initiatoris added, and the mixture is refluxed for 2 hours with stirring to eectpolymerization. The reaction liquid is added dropwise to a 5% NaClsolution, and the resulting precipitate is recovered by filtration, isrepeatedly subjected to thorough water-washing, and is then dried underreduced pressure to obtain polytetracyanobutadiene.

(c) Synthesis of charge transfer complex: The two polymers (a) and (b)are individually formed into 10% acetonitrile solutions and are mixedtogether in equivalent amounts, whereby the mixture immediately becomesbrown. The mixture is then refluxed for 2 hours to form a brownprecipitate. The thus formed precipitate is waterwashed and vacuum driedto obtain a high molecular weight charge transfer complex comprising theN-vinylcarbazolestyrene copolymer and the polytetracyanobutadiene. Thiscomplex is shaped to a sheet with a size of 50 x 50 x 1 mm. to prepare atest piece for electric resistance measurement.

Charge transfer complexes comprising styrene-Z-vinylpyridine copolymersand tetracyanoqulnodimethane (TCNQ) (a) Synthesis ofstyrene-Z-Vinylpyridine copolymers: The copolymers are synthesized inthe same manner as Charge transfer complexes comprisingstyrene-4-vinylpyridine copolymers and tetracyanoethylene (TCNE) Thecharge transfer complexes are synthesized in the same manner as inExample 3. The composition ratio of each copolymer is represented byWeight percent.

in Example 1(a), except that the amounts of 2-vinylpyridine are variedto 1, 5, 10, 25 and 50%.

(b) Synthesis of charge transfer complexes: Each of the copolymerssynthesized in (a) is formed into a toluene solution, is quaternarizedwith 1.5 times the mole of said copolymer of hydriodic acid, is washedwith water to remove liberated iodine (I2) and is dried under reducedpressure. The thus treated copolymer is formed into a acetone solution.On the other hand, LiTCNQ is formed into a 10% acetone solution. To thecopolymer solution, the LiTCNQ solution is added so that the TABLE 4Donor polymer VP/TONE fp 30 C. 30-60 O. Ap 100 4VP:St Aceeptor (molarratio) (S2 om.) K.) 1,000 hr 1:99 TONE 1:1 5. 4 1011 11,000 1 0 5:95TONE 1:1 1. 3X101 9, 800 1.1 10:90 TONE 1:1 5.0X10H 5,000 1.0 :75 TONE1:1 8. 9 105 2, 800 1.1 50:50 TONE 1:1 5.8 103 1,600 1 1 EXAMPLE 5Charge transfer complexes of methyl acrylate-styrene-Z- vinylpyridinecopolymers and chloranil amount of LiTCNQ becomes 1.5 times the mole ofvinylpyridine. The mixture is thoroughly stirred and is reacted at 60 C.for 1 hour to form a complex of each copolymer and TCNQ. The complex isthoroughly washed with Water until no green color due to flame reactionof chlorine has been observed. The complexes prepared in the abovemanner are subjected to electrodialysis and are then vacuum dried toobtain high molecular Weight charge transfer complexes.

Charge transfer complexes of ethyl acrylate-1-viny1-2- ethylimidazolecopolymers and bromanil The copolymerization of ethylacrylate-1-vinyl2ethyl imidazole is effected in toluene solution in thepresence of 0.2% of benzoyl peroxide as a polymerization initiator.

TABLE 3 Donor polymer VP/TONQ 30 C. 30o-60 C. A@ 100 C. Number 2VP:StAeceptor (molar ratio) (S2 em.) K.) 1,000 hr.

1:99 LiTCNQ 1:1 10X10l1 9, 500 1,1 5:95 LiTCNQ 1:1 2.7X101l 8, 300 1. 210:00 LiTCNQ 1:1 1.0)(10J 5, 10U 1. 2 25:75 LiTCNQ 1: l 1.7)(10l 2, Q001.3 :50 LiTCNQ 1:1 7.3X103 1,600 1.3

The composition ratio of each ternary copolymer is represented by weightpercent. The synthesis of the charge transfer complexes is eected in thesame manner as in Example 3.

10 EXAMPLE 9 Charge transfer complexes comprising acrylonitrilevinylacetate-N-vinylthiocarbazole copolymers and tetracyanobutadiene TABLE 6Donor bromanll polymer (molar o 30 C. 30-60 C. Ag@ 100 C. Number EAzV2EIAccepter ratio) (Sl cm.) (D K.) 1,000 hr.

6-1 90:10 Bromanil 1:1 5. 0 109 8, 500 1. 2 6-2 80:20 d0.. 1:1 3.2)(1077, 400 1.1

EXAMPLE 7 15 Charge transfer complexes of butylacrylate-N-vinylcarbazole copolymers and hexacyanobutadiene Thecopolymerization of N-Vinylcarbazole and butyl acrylate is elected in50% benzene solution in the pres- 20 ence of 0.2% ofazobisisobutyronitrile as a polymerization initiator. The synthesis ofthe complexes is carried out in the following manner:

The copolymerization of N-vinylthiocarbazole, vinyl acetate andacrylonitrile is eifected in 50% toluene solution in the presence of0.3% of azobisisobutyronitrile as a polymerization initiator. Thesynthesis of the charge transfer complexes is carried out in the samemanner as in Example 8.

N-vinylcarbazole-butyl acrylate, which has been quaternarized withhydriodic acid, Iis formed into a 10% acetonitrile solution. On theother hand, sodium hexacyanobutadiene is formed into a 10% acetonitrilesolution. The two solutions are mixed together so that the molar ratioof hexacyanobutadiene to N-vinyl carbazole becomes 111.5. The mixture isrefluxed for 2 hours with stirring. Subsequent operations are the sameas in Example 3.

[Charge transfer complexes comprising 2-vinylpyridineoctylvinyl ethercopolymers and tetracyanoethylene (a) Synthesis of 2 vinylpyridineoctylvinyl ether copolymers: To 100 g. of each of 10:90 and 20:80 mixed0 liquids of 2-Vinylpyridine and octylvinyl ether, 100 g. of

TABLE 7 NVCA/ Donor HCNB polymer (molar p 30 C. 30-60 C. Ago 100 C. No.NVCAzBA Accepter ratio) (S2 cm.) K.) 1,000 hr.

7-1 10.90 HCNB 1:1 4. 8 10 8,100 1.3 20:80 HCNB 1:1 2.1 107 7, 200 1.2

NoTE.-HCNB: hexacyanobutadiene.

EXAMPLE 8 Charge transfer complexes comprising 2-ethylhexylacrylate-N-vinylpyrrolidone copolymers and hexachlorobutadiene a 1%sodium lauryl sulfate emulsion is added. The resulting mixture isreacted at 50 C. for 4-5 hours in the presence of a catalyst comprising0.3% (based on the weight of monomers) of potassium perphosphate and0.1% of sodium acidic sulfite. The reaction product is charged intomethanol to form a precipitate, which is then recovered by filtration,washed with water and dried.

(b) Preparation of charge transfer complexes: Each of the2-'vinylpyridine-octylvinyl ether copolymer is formed into a 10% benzenesolution. To this solution is added a 5% benzene solution oftetracyanoethylene in an amount equal to the amount of Vinylpyridine.The mixture is reuxed for 3 hours to obtain a brown precipitate.Subsequent operations are the same as in Example 3.

Norm-HCB: hexachlorobutadiene.

TABLE Donor polymer 2VP/TCNE p 30 C. 30-0 C. Aga 100 C. No. 2VP;OVEAccepter (molar ratio) (S2 cm.) K.) 1,000 hr.

101 10:90 TONE 1:1 7.0Xl0s 7,800 1.2 10-2 20:80 TONE 1:1 8. 5X10" 6, 500l. 4

Norm-TUNE: tetraeyanoethylene.

EXAMPLE 11 on a hot roll at 130 C. with 20 g. of an ethylene-vinylCharge transfer complex comprising p-phenylenediamine as donor andtrinitrostyrene styrene copolymer as acceptor a acetate copolymercontaining 20% of Vinyl acetate. 'Ihe mixture is shaped into the form ofa sheet to prepare a -test piece for the measurement of electricalcharacteristics.

EXAMPLE 14 Plastic thermistors comprising (N-vinylcarbazole-styrenecopolymer)(trinitrostyrene-styrene copolymer) charge transfer complexesand styrene-butadiene copolymers The synthesis of each copolymer iseffected in the same manner as in Example 2(a) and Example 11(a). 20 g.of an N-vinylcarbazole-styrene copolymer and 23 g. of atrinitrostyrene-styrene copolymer are individually formed into 10%benzene solution. The two solutions are mixed and heated to obtain 31 g.of a greenish brown powder of charge transfer complex. 31 g. of thiscomplex and 15 g. of a styrene-butadiene copolymer are individuallyformed TABLE 11 Acceptor polymer p-PDA/TNS gp C. 30-60 C. Ag@ 100 C.Number Donor TNS:St (molar ratio) (S2 cm.) K.) 1, 000 hr.

11-1 p-PDA 1:1 1:1 2Xl0 7, 500 1, 3

NoTE.-p-PDA: p-phenylencdiamine.

EXAMPLE 12 35 into 15% toluene solutions, and the two solutions areHeat-sensitive high molecular weight resistors (plastic thermistors)comprising (2 vinylpyridine-ethyl acrylate-styrene copolymer) (TCNE:tetracyano-ethylene) charge transfer complexes and (ethylene-ethylacrylaet copolymers) The 2-viuylpyridine-ethyl acrylate-styrenecopolymer of each plastic thermistor is obtained by polymerization in50% toluene solution in the presence of 0.2% of azobisisobutyronitrileas a polymerization initiator, The copolymer is formed into a 10%acetone solution, and is mixed with a 10% benzene solution oftetracyanoethylene in an amount of 1.5 times the mole of2-vinylpyridine, whereby the mixture is immediately colored to greenishblack. When the mixture is heated at 60 C. for 1 hour, a complex isformed. 20 g. of this complex and an ethylene ethyl acrylate copolymercontaining 20% of ethyl acrylate are individually dissolved in 500 cc.of carbon tetrachloride. The resulting two solutions are thoroughlymixed and Iblended together. The thus obtained blend is dried by meansof a rotary evaporator, is shaped into the from of a sheet by means of ahot roll and is cut to a size of 50 x 50 x 1 mm. to prepare test piecesfor electric resistance measurement.

EXAMPLE 13 Plastic thermistors comprising (2 vinylpyridine 2- ethylhexylacrylate styrene copolymer) (TCNQ) charge transfer complexes and(ethylene-vinyl acetate copolymers) The 2 vinylpyridine 2 ethylhexylacrylate-styrene copolymer is obtained by polymerization in 50% toluenesolution in the presence of 0.2% of benzoyl peroxide as an initiator.The copolymer is quaternarized with hydriodic acid and is then formedinto a 10% acetone solution. This solution is mixed with a 10% acetonesolution. of LiTCNQ in an amount of 1.5 times the mole of 2-venylpyridine, and the mixture is heated to obtain a greenish blackcomplex. 20 g. of the Icomplex is lineaded mixed and heated.Subsequently, the mixture is dried by means of a rotary evaporator andis shaped into the form of a sheet by means of a hot roll to prepare atest piece for the measurement of electrical characteristics.

EXAMPLE l5 Plastic thermistors comprising (p-phenylenediamine)(trinitrostyrene-styrene copolymer) charge transfer complexes and polyvinylchloride 9 g. of p-phenylenediamine and 20 g. of atrinitrostyrene-styrene copolymer are used to form 22 g. of a brownishpurple powder of charge transfer complex. 2O g. of this complex iskneaded by means of a hot roll at C. with 15 g. of polyvinyl chloride, 7g. of dioctyl phthalate as a plasticizer and 2 g. of tribasic leadsulfate as a stabilizer. The mixture is shaped into the form of a sheetto prepare a test piece for the measurement of electricalcharacteristics.

EXAMPLE 16 Plastic thermistor comprising dimethylcetyl benzyl ammoniumtetracyano-p-quinodimethane of the structural formula FH i enhancing@(TCNQ)T and polyvinyl chloride degree =1200) is thoroughly -kneaded withl0 g. of tridegree P=1200) is thoroughly -kneaded with l0 g. of tribasiclead sulfate and 20 g. of the charge transfer complex dimethylcetylbenzyl ammonium tetracyano-p-quinodimethane. Thereafter, the mixture ischarged with 50 g. of pentaerythritol-ester, as a plasticizer and issubjected to dry blending at 60 C. for 30 minutes. Subsequently, themixture is `kneaded for about l0 minutes by means of a roller heated to-180D C., is taken out in the form of a sheet with a thickness of about1 mm., and is cut to a 13 size of 50 X 50 X 1 mm. to prepare a testpiece for the measurement of electrical characteristics.

EXAMPLE 17 Plastic thermistor comprising stearamide-propyl-dimethyl- 14A 40:20:40 styrene-2-ethylhexyl acrylate-butyl acrylate copolymer isthoroughly -kneaded by means of a hot roller at 140 C., While addinglittle by little to the copolymer 20 g. of the charge transfer complex2-undecylimidazolium tetracyano-p-quinodimethane. After the total amountof hydroxyethyl ammonium tetracyano p qulnOdI- said complex has beenadded, the mixture is kneaded for methane of the structural formulaminutes, is taken out in the form of a sheet with a CH3 thickness of 1mm.,land is cut to a size of 50 x 50 x 1 mm. to prepare a test piece forthe measurement of electrical [CHHMCONHCHZCHzCHQII CH2CH2OH]+(TCNQ) 10characteristics.

3 EXAMPLE zo and ethylene-ethyl acrylate copolymer 1 1 `Plasticthermistor comprising di(di--hydroxyethylamino- 100 g- Of .an 80'20ethlflene'ethyl acry ate copo yer ethyl) o phthaldiamidetetracyano-p-quinodimethane (trade name DOY 6129) 1s. kneadefl by meansof a Ot and styrene-butadiene-acrylonitrile copolymer (ABS roll at 120C. while adding little by little to the copolymer 1D resin) g. of thecharge transfer complex stearamide-propyl- E imam/1 hydroxyethylamm0nium tetracyano p quino 100 g. or a styrenebutadiene-acrylonitrilecopolymer dimethane. After the total amount of said complex has (ABSresul) Powder 1S .dn/blended at 60 C- for 30 been added, the mixture isfurther kneaded for 15 minutes, minutes by means of a f1bb0n-b1endefWlth 20 g' Ofthe is taken out in the form of a sheet with a thickness of20 charge transfer Complex of d1(dl''hyffyethylammo' 1 mm and is Cut toa Size of 50 X 50 X 1 mm to prepare ethy1)ophthaldiamidetetracyano-p-quinodimethane, of a test piece for the measurement ofelectrical characterthe structural formula mics' ooi?? on CH g o H on HEXAMPLE is I 2- 2- 2 4 )2 Plastic thermistor comprising-hydroxyethyl-Z-methyl- (TCNQM imidazolium tetracyanoquinodimethane andethylenevinyl acetate copolymer CO-CHZ-CHZ-wiEIiOHn 100. 0f 82118ethyl'el'leVIll/l acetate copolymer (trade 30 which is anelectroconductive plasticizer. Subsequently, name. Eyerexn630) ischarged with 0.5' g- Of all ansi" the blend is injection-molded, by useof a small size inoxldant 101101 Produced by Shen Chemleal CQ) agld 1sjection molding machine, into a metal mold of 50 X 50 x 1 tho'roughlykneaded by means 0f a hot rou at 130 C" mm., while maintaining thecylinder temperature at `180" while adding little by little to thecopolymer 25 g. of the C. to prepare a test piece for the measurement ofelec. charge transfer complex -hydroxyethyl-2-methyl-1m1d- 35 tricalCharacteristicsazolium-tetracyano-p-quinodimethane. After completion ofthe addition of said complex, the mixture is further EXAMPLE 21 kneadellfOr 15' IIllIlUeS, 1S faken Out in the fOfm Of a Plastic thermistorcomprising stearamide-propyl dimethylsheet with a thickness of 1 mm.,and is cut to a size of hydroxyethyl ammonium tetracyano p quino. 50 x50 x 1 mm. to prepare antest piece for the measure- 40 dimethane andepoxy resin ment of electrical characteristics.

.To 100 g. of an epoxy resin (Epikote 828) is added EXAMPLE 19 withthorough stirring 15 g. of the charge transfer com- Plastic thermistorcomprising 2-undecylimidazolium tetraplxltearlnde prop y1 f di-net??hydplythyl mcyanoquinodimethane of the structural formula m m mracyallop-qumo Ime ape W .1c 1S au e-ec' troconductive curing agent. Themixture is charged into |r==` an optional mold for sheet molding and iscured in about N N 2 hours in a thermostat at 100 C. The resulting sheetis \C/ (TCNQ) cut to a size of x 50 x 1 mm. to prepare a test piece lfor the measurement of electrical characteristics. CMH 50 Thecharacteristics of the plastic thermistors of Examand 40:20:40styrene-Z-ethylhexyl yacrylate-butyl acrylate ples 12 to 21 aresummarized in Table 12.

TABLE 12l Example 3 C. 3 6 C. Number Charge transfer complex Matrixpolymer l(1)12 3m.) D GOK.) Alllli?) h?.

12 (Znyl'llrvlyidine-ethyl acrylatestyrene)(tetracyano-Ethylene-ethylacrylate eopo1ymer.... 8.0 10s 7,500 1.2

y S 13 (2-vinylpydineethylhexylaciylate-styrene).(tetra- Ethylene-vinylacetate colpoymeizm. 3.0 108 7,000 1.1

cyano-p-quinodimethane(N-vinylcarbazole-styrene).(trinitrostyrene-styrene) styrene-butadienecopolymer 1. 5 10J 9,000 1.3(p-Phenylenediamine).(trinitrostyrene-styrene) Polyvinyl chloride 7.5108 8,000 1.2 16 Dimethylcetyl benzyl-ammonium tetracyano-po 7,500 1.5

quinodimethane. i7 Stearamide dimethyl hydroxyethyl-mnmoniumEthylene-ethyl acrylate copolymer 5.0 108 7,000 1.1

tetracynno-p-quinodimethane. 18 -Hydroxyethyl-2-methylimidazoliumtetracyano- Ethyl-vinyl acetate copolymer 1.1X109 8,500 1. 4

quinodimethane. 19 2-undecylimidazolium tetracyanoquinodimethaneStyren1e-t2ethyl1hexylacrylate-hutyl 4.0X10E 8,200 1.6

ry .o o m 20 Di(di--hydroxyethylamino-ethyl)-phthaldi-Stigreng-llftaldielle-xerylonitrile 1. 5 10 9, 000 1.2

amide tetxacyano-p-quinodimethane. copolymer. 21Stearamide-propyl-dimethyl--hydroxyethyl Epoxy resin. 2.0X10f 8,000 12.0

ammonium tetracyanc-p-quinodimethanc.

Convent'onal 30 C. 3 60 C. A C example l Charge transfer complex Matrixpolymer sa@ cm) 0 K.) ge?) hr 1 Vinylpyridine tetracyanoethylene None1.0X10 3 1,000 12.0 2 Carbon black Nitrile-butadiene rubber 2.5 1032,000 3.0 3 N-methylquinolinium bromide Polyvinyl chloride .5X10 10,00015.0 4 Carbon black Methyl acrylate graft polymer. 3.0 104 3,000 3.5

EFFECTS (1) Characteristics of plastic thermistors and methods for themeasurement thereof The electrical charactersitics of the plasticthermistors according to the present invention are set forth in Tables2-12 in comparison with those of conventional thermistors.

In the table, p30 C. (0 cm.) shows a value of volume resistivity at 30C.; and 3060 C. K.) is an indication of temperature detectionsensitivity of plastic thermistor and is represented by the formula To(l) In calculating, according to the above formula, the temperaturedependence of volume resistivity at temperatures between 30 C. and 60C., p0 is a volume resistivity value at 30 C.; (p is a volumeresistivity value at 60 C.; To is 303K.; and Tis 333 K.

Arp 100 C. 1000 hr. shows a variation ratio of volume resistivity valuesin the case where direct current has been continuously applied in an airatmosphere at 100 .C. for 1,000 hours, yand is represented by theformula A@ 100 o. 1000 hr.=1 do (2) Features of plastic thermistors (l)Electronic conduction: The plastic thermistors of the present inventiondisplay their effects according to conduction mechanisms ascribable toanion radicals or charge transfer electrons formed from the chanrgetransfer complexes employed, and therefore current carriers areelectrons or halls. Accordingly, the plastic themiistors of the presentinvention do not cause any polarization even when direct current isapplied thereto. In the cornplexes of the present invention, there isobserved no such absorption current as seen in the case where directcurrent is applied to ionic conduction materials. Furthermore, even whenthe polarity of electrodes is reversed, no maximum current is observed.Thus, the present complexes are same in conduction behavior as inorganicsemiconductors. For the above reason, the plastic thermistors of thepresent invention are usable in electronic circuits. When the presentplastic thermistor is inserted between two wires of an electric blanket,one wire can act as heater. The temperature is detected by the variationof resistivity between two wires by applying direct current and one wireis heated by applying alternative current. By virtue of the presentplastic thermistors which do not polarize even when direct current isapplied thereto, it has rst become possible to produce heat-sensitiveheaters.

(2) Volume resistivity and temperature characteristics: In accordancewith the present invention, it is possible to produce thermistors havingsuch characteristics as volume resistivity values at room temperature of5.8 l03 to 3.1 1012 (S2 cm.) and thermistor temperature coefficients at30-60" C. of 1,500 te 14,800 K). Particularly, when the content ofelectron donor group in the same copolymer composition is varied, it ispossible to freely produce thermistors having volume resistivity valuesof 103--1011 Q cm. and thermistor temperature coeicients of l,500-9,000K.), as shown in Example 3. In the case of organic semiconductors, ingeneral, the thermistor temperature coecients become lgreater withincreasing volume resistivity. According to the present invention,thermistors having desired volume resistivity values and temperaturecoeicients can be freely obtained. In case a thermistor is desired to beapplied to, for example, an electric blanket, the detecting wire becomesnecessarily longer (10 m. or more), and therefore it is desirable, fromthe standpoint of prevention of self-heat generation also, to use athermistor having a volume resistivity at room temperature of about 1090 cm. and a temperature coefcient of about 8,000 K. The plasticthermistors of the present invention which have the abovementionedcharacteristics are high in temperature coefficient, and the detectionsensitivity thereof reaches as high as 5-6 times the sensitivity ofmetal oxide thermistors.

(3) Heat resistance stability in volume resistivity: The heat resistanceof the present plastic thermistors Was evaluated by continuouslyapplying direct current at C. for 1000 hours to obtain volumeresistivity values of 1.0- 1.6. However, when direct current is appliedto Aconventional thermistors, volume resistivity values vary from3.0-3.5, in the case of those which are superior in quality, to12.0-15.0, in the case of those which are obviously ionic conductive.The stableness in volume resistivity values of the present plasticthermistors is ascribable to the points (l) the conduction mechanisms`are electronic and (2) the plastic thermistors themselves areconductive polymers (Examples l-l l) or have been molecularly dispersedin matrix polymers. It is considered that, in the case of particledispersion, like in conventional Examples 2 and 4, the molecularmovement of matrix polymers necessarily becomes vigorous at elevatedtemperatures and therefore uniform inter-particle contact cannot beattained to bring about unstableness in electric resistance. It is athird characteristic of the present invention that the above drawbackhas been overcome by use of groups lcapable of being molecularlydispersible with ease or by adoption of polymerization.

(4) Moldability and flexibility: All the plastic thermistors shown inExamples l to 2l have moldability and tlexibility. Since the flowproperties of polyvinyl chloride compounds of general use are as shownin conventional Example 3 (FIG. '3), the plastic thermistors of thepresent invention have properties equal to or more easily process ablethan plasticized polyvinyl chloride compounds. Accordingly, they can beshaped into any forms of lines, sheets and ribbons according to theobjects of temperature detection appliances employed.

As detailed above, the plastic thermistors of the present invention areheat-sensitive materials which are higher in detection sensitivity thanthe conventional thermistors, can be produced at low costs, are moldableinto any forms, and have ilexibility. Particularly, the point thatdirect current is applicable is the greatest industrial effect of thepresent plastic thermistors over the conventional heatsensitive highmolecular weight resistors.

We claim:

1. A heat-sensitive high molecular weight resistor comprising a highmolecular charge transfer complex alone or dispersed in a high molecularmatrix,

said high molecular charge transfer complex formed from an electronacceptor selected from the group consisting of homopolymers andcopolymers of maleic anhydride, tetracyanobutadiene and trinitrostyreneand an electron donor selected from the group consisting ofp-phenylenediamine and copolymers containing a member selected from2-vinyl pyridine and N-vinylcarbazolet References Cited UNITED STATESPATENTS Acker et al 252-500 Harris 252-500` Lupinski et al. 252-500Matsunaga 252-500 18 3,428,892 2/1969 Meinhard 252-500 3,441,505 4/ 1969Schmiedel 252-500 3,448,177 6/1969 Goodings et al 260-895 OTHERREFERENCES Labes et al.: Journal of Chemical Physics, vol. 33, No. 3,:September 1960, pp. 868-871.

DOUGLAS I. DRUMMON-D, Primary Examiner U.S. Cl. X.R.

260-78.4 R, 80 P, 88.7 A, `874, 887, 892, 894, 895, 899

UNITED STATES PATENT oFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,632526 l Dated January 4, 1972 i Inventor s) Kazumasa YAMAMoTo et al It iscertified that error appears in the above-identified patent 4and thatsaid Letters Patent are hereby corrected as shown below:

' One of the four Japanese applications in the Claim for ConventionPriority is omitted and should be inserted as follows:

signed and Sealed this 27th day of Jun 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer' Commissionerof Patents USCOMM-DC 603764569 fr u.s. GOVERNMENT PRINTING OFFICE: |9690 366-334

